Saturday, August 27, 2016

I want to share all of these with my classes during kinematics! The NY Times posted these great Olympic moments in composite pictures. Often simple motion is modeled for students by showing the object in successive photos in the same image. By comparing the distances between the object over time students can get a sense of how quickly it is moving.

When viewing the page you will scroll down but will actually be moved to the right in order to see their full width. Some of the images like the one above seems to be taken in even intervals of time and would therefore be easier to compare. So how can you use them? Let's take a look:

Christian Taylor's gold winning triple jump:

Notice that Taylor's body makes a parabola while he's in mid air for the long jump. What might be surprising is that there is also a clear parabola in his bounds before his big jump. You can trace over the image along his center of mass and show students the parabola shape. You can also point out Taylor's change in position at the end during his jump and discuss his center of mass.

"On match point in their semifinal, the Brazilian team of Barbara Seixas
and Agatha Bednarczuk ousted Kerri Walsh-Jennings and April Ross of the
United States."

There are great parabolas to be seen in the projectile motion of this volleyball. The volleyballs are closer together at the top of the parabola because it is moving slower and will not travel as far in between each picture.

Derek Drouin's winning high jump:

This image shows Drouin's change in speed as the distance between each changes. There is a great parabola during his high jump and you can see him change the position of his center of mass.

Laurie Hernandez on the balance beam:

I would use this to show students that even when it seems like she's floating on air her center of mass is always supported by a base underneath her. In the first few images show her feet underneath her. The fourth shows Hernandez supported briefly by her hands. As she dismounts you can see a parabolic shape if you follow her center of mass through her flip.

Anytime you can relate what you're studying to the "real world" for your students is a win.

Sunday, August 14, 2016

I will give you a few moments to catch your breath before providing the details. For those of you who are not excited after reading the headline, here is why you should be. The American Physical Society Division of Plasma Physics offers one of the best educational outreach programs of any professional society. They know what professional development is useful to teachers and how to make teachers feel as important as they really are. If you have been lucky enough to attend one of their meetings when it was in your area then you know what I am talking about. This year's meeting will be in San Jose, California. That makes it worth the drive for thousands of science teachers from Sacramento to San Luis Obispo. They offer 3 days of educational outreach at their annual meeting, Science Teacher Day for teachers and the Plasma Science Expo for students.

Science Teacher Day will start at 8:00 AM on November 1 at the San Jose Hilton, registration is open now. This event will be popular and registration is limited so do it early. After an introductory breakfast, it is off to Plasma 101 for Session 1. Plasma 101 has two levels, one for middle school teachers and one for high school teachers. The remaining workshop presenters can now build on what was learned in Plasma 101. After Session 1, teachers pick 2 from the 6 workshop choices that are offered in Sessions 2 and 3. These workshops are full of ideas that can be used in the classroom to teach topics like the electromagnetic spectrum, properties of light, Newton's Laws, astrophysics, and plasma physics. They are appropriate for both middle and high school teachers. The workshops are conducted by the same scientists that are participating in the conference. You can read the workshop descriptions on the APS DPP Outreach website. After the workshops a white-tablecloth luncheon is served and the teachers are treated to a keynote talk by one of the scientists. All teachers go home with a goodie bag filled with educational materials. Here is what one teacher had to say after the Salt Lake City Science Teacher's Day:

Following Science Teachers Day is an open house consisting of educational exhibits by many of the institutions that participate in the conference. This Plasma Science Expo is like a hands-on science museum where each exhibit is staffed by working scientists. Teachers are invited to bring their classes to San Jose's McEnery Convention Center on either of these two days, November 3 and 4. It is open to the public for free on November 3 from 6:00 to 8:30 PM. Just like Science Teacher Day, registration is required and limited. There are some funds available to help pay for buses and substitute pay, so register early.

As part of my role as a Faculty Scholar at LLNL, I have attended the APS DPP conference in Denver, Dallas, Chicago, and Salt Lake City to help conduct one of the workshops. I was able to stay for the Plasma Science Expo in Chicago to help staff the LLNL booth. I work with Don Correll, the former head of the Fusion Energy Program at LLNL and Steve Allen, a magnetic fusion scientist at LLNL and General Atomics. In addition to being leaders in their field, they are both committed to helping improve science education through outreach activities like those at the APS DPP meeting. I am excited about working with them again in San Jose after a 5 year hiatus. We will be conducting the Light and the Nature of Matter workshop at the Science Teacher Day. I hope to see you there. If you have questions, see the links in this post or contact Deedee Ortiz-Arias at dortiz@pppl.gov or (609) 243-2785.

Friday, August 12, 2016

There are a wide variety of different school situations out there with different funding situations. You may have a one to one device classroom and everything you want (and I might kind of hate you ... not really, but kind of). Or you may have to supply everything yourself for your students. No matter your situation, you have probably at some point asked someone for something for your classroom. Even though you are coming from a good place it can be a little uncomfortable to beg for money or supplies. You get better at it with time, and as you learn about more resources. So here are a few resources and suggestions to help you on your way:

Back to school time is the season for donations and generous families. The advantage to asking for donations of money or materials this time of year is that literally everybody is doing it. Families are donating to art and the PTA and education funds and buying school supplies etc. This could also be a disadvantage as families feel overwhelmed and financially taxed.

So how can you still get stuff and families still get to eat? (And if you think that is hyperbola think about how many children in California qualify for free and reduced lunch.) One key is to ask for stuff not money. Our department has a common donation request letter that explains why we need the money (duh) and asks for $20. The back of the letter is filled with stuff that we would love to take. Sometimes parents have unique connections to get us these materials for us. Things we ask for: scrap wood, tools, holiday lights, plastic utensils, mini fridges, toilet paper tubes, hand soap, paper, pencils, etc. One year a parent worked for Dow and gave us enough hand soap to last the Chemistry teachers for years. I tell students that if they can't donate money I would love for them to grab an extra ream of paper or if they have a spare toaster to take apart I'm happy.

Getting to know your students and their families can also open doors. Take advantage of unique resources from families. My TAs used to help block out my windows for our light unit by covering the windows with black garbage bags. One TA got half way through the job and said "I have something better for this. I'll finish it tomorrow." He came back the next day with black posterboard that had been laminiated and fit to cut to size for each of my windows. Turns out his dad owned a print shop. It didn't cost the family much but for me it was priceless.

Crowd source your needs. If you have not used DonorsChoose.org before I highly recommend it. I have gotten several thousand dollars worth of materials through Donors Choose donors over the years. When you create an account you have a certain number of points and larger projects require more points but most projects are only worth two or three. I have had local businesses and anonymous donors fund my projects as well as people from across the country. I have a link to my Donors Choose page at the bottom of my emails and on my class website. If the project is of particular high need (as in without it we aren't completing a popular project this year) then I may send out an email to my students and their families asking them to help spread the word. Some teachers also share projects via their own social media sources. GoFundMe is another crowd source option that does have an education section. GoFundMe is not education specific and can be used for a variety of things.

Know what you want. Dean Baird told me as a new teacher to keep a folder with my wishlist. He suggested we rip the pages right out of the catalogs with what we wanted circled and just toss it into a folder. "Sometimes," he said, "there is extra money that just has to be spent that day. Be the one that has their list together so that you're the one to take advantage." Turns out, he was right. My second or third year I had a lot of English Learners in my class and was asked to attend a training day to learn some strategies to help them. While there I talked a lot with one of the leads of the program who asked if there was material he could order that would help his students learn better in my class. Someone was actually asking for that list Dean made me keep! And I had it ready.

Ask, and you shall receive. It seems so obvious but it is true. Asking for whatever you need is at least the first step to getting it. For years I wanted a bowling ball to make a bowling ball pendulum of my very own. I finally decided I wanted one bad enough to ask. I wrote a very formal letter (on letterhead even) explaining the many uses I had for one bowling ball in my classroom, included my contact information and mailed it to a local bowling alley. About a week later I got a call "Hey, you asked for a bowling ball? For a science class?" I eagerly agreed. "Ummm, do you want twelve?" As I explained in my bowling ball post, I took them. Another time I needed a few pieces of scrap glass for a Mohs hardness test so I asked a local hardware store for broken glass they might have laying around. They obliged, after I explained why I needed shards of glass. There is a "Sale" section of Home Depot's lumber department which has wood at a discount. If its not labeled, and you play the teacher card, it might be even cheaper. (not an official policy)

Recycle! Reuse! I've already said I'm a hoarder but because I hoard I don't have to repurchase. Some examples: the base wood for my Rube Goldberg project is reused year to year after the machines have been removed; the magnet and magnet wire in my "Make A Speaker" lab are unwound and used again and again; brads and paper clips from my Electric Building Project are ripped from student projects and kept for the next year. I even make TAs cut out the used pages of notebooks if half or more is still blank and keep them in reserve.

Make it yourself. There are a few demos or classroom tools that you can make yourself instead of purchasing. If you have the know how and are inclines to do so DIY it!

There isn't much in the field of teaching that is easy, but much gets easier with practice. So if there are things that you want for your students, try asking for others before spending your own money. Don't worry, I'm sure you'll still spend hundreds of dollars as a teacher over the course of your career so you don't have to feel guilty. ;)

Thursday, August 11, 2016

I was so happy to see that baby Boomer Phelps, son of Olympian Michael Phelps, wearing hearing protection at the games this week. Since the announcer are drowned out while I'm watching at home I imagine the aquatic center is deafening. I've been looking but can't find decibel levels from this week's competition.

Tuesday, August 09, 2016

In our Thermodynamics unit students observe a drinking bird's motion to try and figure out how it works. I ask them a series of questions to guide them but several come to the wrong conclusion. Now I set up drinking birds with hot water, ice water, isopropyl alcohol and one without a cup on the second day. I ask students to apply their original explanation to the second day and that helps a few more of them. I tell students that a doctorate level thesis was written on this seemingly simple bird so it's ok if they need a one time to understand it. There are several common wrong answers:
- The liquid from the cup goes into the bird through the beak.
- Heat from the room expands the gas in the bottom bulb forcing the liquid up (Close, can be seen if you hit the bottom with a hair dryer or hold it in your hand briefly. Try to avoid doing this in front of the kids to avoid this misconception.)
- The liquid inside the bottom bulb is heated by the room and expands.

The birds are occasionally handled too rough. I mounted one such poor bird and will add a little tombstone under it. I scraped the felt off part of the head so students could see how the top bulb was connected to the bottom one. I would like to take all the felt off of a functional head for students to compare as well. I had to add some hot glue inside the head (the cloudy white you see) in order to keep the broken fragments together. I hope to add a plaque:

Others have covered this phenomenon extensively; such is the bright and microscopic nature of Olympics reportage. There are segues and human interest stories to be filed for the interstices of the wall-to-wall coverage.

What are those mysterious circles visible on athlete's bodies? The answer is: cupping hickies/bruises.

Not only will Phelps continue to cup, but look for the cupping hickies on other athletes. All events; many nations. Trust that the practice will filter through to college and eventually high school athletes. Without the benefit of evidence, the practice offers a mystical advantage that promises adherents a competitive advantage. Who will dare put him herself at a "disadvantage" by not jumping on the band wagon?

The takeaway is that there will always be something. Some untested, evidence-free "edge" that athletes will flock to. Copper bracelets, magnet bracelets, hologram bracelets, aqueous metal-infused necklaces. This month: cupping. An objective observer might hope for some placebo effect. But that's all anyone can hope for.

There are many more links to be perused at one's leisure. If you see a nice one, let me know.

Monday, August 08, 2016

I spent part of my vacation with my son and other family and friends fishing. We were staying on the shore of a very large body of water on the Minnesota/Canadian border called Rainy Lake. The weather, fishing, and companionship were all fantastic. One morning the winds were very light and the sun was shining over the chilly lake water. I noticed something strange on the horizon. There appeared to be trees floating in the sky.

This did not look like the typical mirage. I recalled something about a type of mirage that is often seen over ice or cold bodies of water. I kept a watch on the horizon as we pulled one walleye after another into our boat. I had my Cannon HD video camera that can take pretty good 8 MB low-light stills. Over the next hour or so I took pictures of some other strange sights on the horizon.

Some small islands and parts of the shoreline joined the trees in the sky. We were witnessing the formation of superior mirages. These form when there is a layer of cold air below a layer of warm air. The cold lake water was keeping the air near it cooler than the air above, forming a temperature gradient known as an inversion layer. Light from distant objects was bending down as it encountered the less dense warmer air. The path of the light from the objects can follow the curvature of the Earth, allowing objects beyond the horizon to be seen. This effect can be demonstrated by partially dissolving sugar or corn syrup in an aquarium. If done carefully, the density gradient of the sugar mimics that of the inversion layer, causing the path of a laser beam to bend down.

Inversion layers are stable, allowing the mirages to be seen for long periods. They also lack the shimmering of inferior mirages often seen on the road on a sunny day. This makes superior mirages seem more real and provoked an eerie feeling. Some of the images I had a hard time explaining. This one shows a superior mirage forming in front of an island.

On returning from my trip I did some reading about mirages to learn more about what I had seen. Superior mirages have been reported throughout history and have sometimes altered it. Early explorers trying to find the Northwest Passage turned around when they saw a mountain range looming in the distance. Later explorers returning to the same place saw no mountains. They had probably been discouraged by a complex superior mirage known as a Fata Morgana. Another stranded group of arctic explorers saw the polar night end two weeks early when the sun formed a superior mirage over the ice. In fact, anytime you watch the sun rise or set its image is being refracted around the curve of the Earth by the density gradient always present in the atmosphere. This is technically not a superior mirage because the density gradient is pressure, not temperature-based but the effect is the same.

There are other fascinating stories of superior images and Fata Morgana sightings that are worth reading. I found the Wikipedia article about mirages and Fata Morgana useful, as well as this website and this one. I am now better prepared for the next time I observe this unusual phenomenon. Another illusion on Rainy Lake was self created. When posing with my 23-inch walleye, we found we could make it look a lot bigger with some creative posing. If anyone from the Fish and Wildlife service is reading this, we did throw it right back in the water.

Friday, August 05, 2016

The last on my School's Out, Tools Out build list was a two way mirror box. Once while visiting Tap Plastics I saw a small black box on a shelf.
There was a mirrored front and a sign that said "Flip the switch!" When I did a light bulb appeared inside the black box as it turned on. Turning it off made the light bulb "disappear." I bought a square foot of two-way mirror acrylic on the spot for about $20 and added it to my mental build list.

This summer I finally built it. I used an old bureau bookcase we cleaned out of our garage because it already had routed tracks for a sliding door. I planned on building it myself and just needed to borrow my father-in-law's chop saw to make the angled cuts. Well, he's retired and likes projects so he ended up building it for me. It was a hard gift to refuse a few weeks before school started.

In retrospect I would have liked to spray paint the inside of the box black before adding the mirror. I can still paint it black by hand. The box has to have a sliding panel on the back in order to access the light bulb for replacement. I built a simple light base using a plastic lampholder, in-line cord switch and a plug at the end with some extra wire I had. The wire could be pulled through a hole in this back panel but light leaks are an issue so use some kind of gasket on it. I would like to find a remote operated light for dramatic effect so I don't have to be next to the box flipping the switch.

You can see in the picture at right the actual light bulb in the front and its reflection in the back. The two-way mirror has a mirrored finish on only one side, I put this mirrored side to the inside. As far as I could tell it would work either way but this way the more delicate mirrored side is inside the box. You can see the groove that was used for the back panel.

In order for the box to work well the inside has to be as dark as possible and the room it is sitting in as bright as possible. If you look closely enough you can barely see the light bulb inside before it is turned on. In these pictures below I enjoyed surprising my kids. The room lighting did not change, my camera however did change its light settings making the outer room look darker because of the brightness of the bulb.

Here's a video, although again there is a big change in the camera light settings. I swear I wasn't simultaneously turning off the room lights. You can see the inside of the box is unpainted.

Students always ask about two way mirrors when we talk about light reflection and refraction. We talk about transparent vs translucent vs opaque materials and I ask students which one describes a mirror. Most students correctly identify it as an opaque material, something that reflects or blocks all of the light letting (almost) none of it through the mirror. "But what about a two way mirror?!" Then a series of comments like "This one time in this one movie..." follow. Now I can pull this out from behind my demo table with a "ta da" flare and demo it on the spot.

Thursday, August 04, 2016

You've probably seen this video of Luke Aikins jumping out of a plane from 25,000 feet without a parachute. Knowing the physics behind it doesn't make it any less impressive:

There are several videos online but I like this one with the height
gauge at the side. This video shows his top speed at 150 mph but this LiveScience post and a few other sources quote a human's terminal
velocity around 120 mph or 53 m/s. Aikins says both 150 mph and 120 mph
in this NPR interview about how they prepared for the jump. Wired also discussed some of the physics behind Aikins' jump, focusing on air resistance and terminal velocity. The net is 100 feet by 100 feet and held 200 feet above the ground by four cranes at each corner. In the interview Aikins refers to the giant net as his parachute, its just below him instead of above him.

Remind students it Aikins were to go from 120 mph to 0 mph by hitting the ground he (probably) isn't surviving. So how can he go through the same change of speed in the net and survive? Hopefully you hear a chorus of students saying that time is a factor and it has been its extended by the net. If you bring up this example in your motion unit your students will probably refer to the acceleration equation. A smaller time value means a larger acceleration (and a larger force); an extended time will produce a smaller acceleration. Students can practice their unit conversions to find Aikins terminal velocity in kilometers per hour or meters per second.

Aikins flips on to his back, so that he can land without snapping his neck, at 2:30 in the video above. I downloaded the video and edited it down to his landing in the net. In this edited version the first contact with the next is seen at 2:24 seconds. As Aikins falls into the net the edges don't stay taught (another talking point) so its tough to call when he comes to a full stop and when the lowering of the net starts. I called it at 4:00 seconds making the time it takes him to stop in the net 1.76 seconds. If students use 53 m/s they will find a decceleration for Aikins of about -30 m/s^2 or about 3g.

With the same information students can calculate Aikins kinetic energy just before he hits the net. All of that kinetic energy is converted to work done on the net and to elastic potential energy of the net. You will have to make some assumptions about Aikins mass and the stretch of the net. The NPR article includes these two pictures of the net before and after Aikins jumps into it, he's the speck in the top of the left side. I set them side by side and drew a line over to show 200 feet about the ground. The perspective will make it difficult to exactly determine the height of Aikins when he stops completely, you can discuss with students how best to do so.

What else can you discuss? Momentum! This is just like a car traveling at high speed that has to be stopped. It can hit a wall in a short time and be destroyed or it can be stopped over a (relatively) long time and suffer minor damage. Again students can calculate Aikins' change in momentum based on the information they find and making a few simple assumptions.

Obviously the experts that helped build it went into a little more detail but its an interesting piece of Physics not beyond basic mechanics principles we teach our students.

Disclaimer

The views expressed in this blog are those of the post authors and commenters. They are not necessarily those of The San Juan Unified School District, The California Department of Education, Pearson Education (or any of its imprints).